Well, in general, "kill all anything" cards are generally disliked by the community. They're hard to balance, as they either lay waste to a rush or do the opposite to a stall.
Well that's why I'm trying to balance it. Also do remember, most rush decks with unprotected creatures can be wrecked pretty quickly with just a pair of Rofs. As for rush decks with protected creatures (quintessence or burrowed) perhaps I change this card so it can't get them either (it can't target them now as it is, but it can target creatures of the same element).
As for stall decks, removing all of their quanta for a full turn can be devastating for them. stall decks often require a balance of creature control cards, shields, and usually permanents for buffs. just one turn without quanta means the opposing player can do whatever they want with no fear of response for the next turn. Wiping quanta for a turn also means it would take a turn or two after that to get the quanta back in a rainbow deck, and it still would probably take at least one turn after in non rainbows. That is invaluable time to the opposing player.
Also even the upped card only kills creatures of one element. many decks have more than one element's creatures.
Still, I know what you mean, it is a tough one to balance.
